There is great interest today in using digital games in education as they are seen to have a positive effect on the children who use them. Such games may offer an alternative for teachers as a play-based learning approach. This is particularly true for children with hearing disabilities, who face enormous challenges in learning literacy; digital games could provide the effective means to motivate them. The design of a serious game for a child with a hearing impairment, however, involves a set of principles that needs to be taken into account. Based on a group of activities conducted with children with hearing disabilities, a set of existing principles was identified. Others were added using information gathered about the user. These principles were then applied in the design of a serious game called "Literacy with Fitzgerald".